Musnad Abu Ya'la al-Mawsili 109:113

Ahmad ibn Ibrahim al-Mawsili narrated to us, Hafs ibn Ghiyath narrated to us, from Ash'ath, from Ibn Sirin, from Abu Bakrah: I heard the Prophet, may Allah bless him and grant him peace, delivering a sermon on the Day of Sacrifice while upon his riding beast at Mina.